2-cyanoacrylate-based composition, method and agent for evaluating curing thereof

ABSTRACT

A 2-cyanoacrylate-based composition comprises a coloring material that changes color with curing of 2-cyanoacrylate. The composition has good visibility and excellent workability as it is colored before curing, and changes color with curing as it becomes colorless or light-colored after curing, thereby providing bonded, filled or surface treated portions with good appearance.

CROSS-REFERENCED APPLICATIONS

This application is the National Stage of International ApplicationPCT/JP03/14058, filed Nov. 4, 2003, the complete disclosure of which isincorporated herein by reference, which designated the U.S. and thatInternational Application was not published under PCT Article 21(2) inEnglish.

TECHNICAL FIELD

The present invention relates to a 2-cyanoacrylate-based compositionthat changes color with curing, in particular to a 2-cyanoacrylate-basedcomposition that, before curing, is colored so that portions subjectedto adhesion, filling or surface treatment can be easily visuallyrecognized and, after curing, becomes colorless or light-colored so thatportions subjected to adhesion, filling or surface treatment have goodappearance, and to a method for determining the curing of the2-cyanoacrylate-based composition and an agent for determining thecuring of the same.

BACKGROUND ART

As 2-cyanoacrylates are instantaneously anionically polymerized to formrigid polymers, they are widely utilized as instantaneous adhesives,rapid-curing fillers and the like in various industries, medical fields,leisure fields and houses. Cured products of 2-cyanoacrylates aregenerally transparent and colorless and have advantages in that portionssubjected to adhesion, filling or surface treatment are inconspicuousand do not spoil appearance.

However, as 2-cyanoacrylates are transparent and colorless even inliquid form during coating and filling, they have disadvantages in termsof handling in that sites which have been coated or filled with them arehard to be distinguished and the amount of coating is difficult to bedetermined.

Conventionally, various methods have been investigated in order to solvethese problems. For example, these methods include a method in whichcoloring materials are added to 2-cyanoacrylates (U.S. Pat. No.2,784,127 specification (column 5)) and a method in whichanthraquinone-based coloring materials that have good color developmentproperties, are blended with 2-cyanoacrylates (U.S. Pat. No. 3,699,076specification (columns 3-5 and 8)). In addition, they include a methodin which coloring materials having a structure that emits a specificfluorescence are used so as to visually recognize it by irradiation withultraviolet rays (U.S. Pat. No. 4,405,750 specification (columns 4-5))and a method in which coloring is carried out by adding salts of basicdyes with various acids (Japanese Patent Laid-Open No. 52-65531 (claims,and page 3)).

When 2-cyanoacrylate-based compositions are used for adhesion, filling,surface treatment or the like, it is of interest whether or not coatedadhesives and cured products, particularly their portions or parts thatwill be shown or exposed after curing can be clearly determined visually(hereinafter referred to as “visibility”), in as much as the presentinvention focuses on appearance after curing. Namely, for applicationsin which workability is of interest, it is preferred that2-cyanoacrylates are colored before curing to an extent that visibilityis good. On the other hand, it is preferred that cured products andtheir exposed parts are inconspicuous, that is, transparent andcolorless or nearly colorless, in consideration of appearance aftercuring.

However, with regard to the incorporation of coloring materials,conventional visible coloring materials improve the visibility duringcoating, but are still disadvantageous in that they also color curedproducts and spoil the appearance. Moreover, fluorescent coloringmaterials express visibility by irradiating them with ultraviolet rays,but have several defects, for example, in that an ultraviolet rayirradiation apparatus is needed and ultraviolet rays may affect humanbodies.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to eliminate the abovedisadvantages of prior art and provide a 2-cyanoacrylate-basedcomposition that changes color with curing, namely, is colored beforecuring so as to provide excellent visibility and workability, and iscolorless or light-colored after curing so as to provide excellentappearance for portions which have been bonded, filled or surfacetreated, as well as to provide a method for determining the curing ofthe 2-cyanoacrylate-based composition and an agent for determining thecuring of the same composition.

As a result of intensive researches for the purpose of solving the abovedescribed problems, the present inventors have completed the presentinvention by finding out that a 2-cyanoacrylate-based composition withwhich a specific coloring material is blended is colored before curingand turns colorless or light-colored after curing, thereby surprisinglyalleviating all the above problems.

Namely, the present invention provides a composition comprising a2-cyanoacrylate with which a coloring material that changes color withcuring of the 2-cyanoacrylate is blended. It should be noted in thepresent invention that the sentence “change(s) color with curing of the2-cyanoacrylate” means that color changes as the 2-cyanoacrylate-basedcomposition is cured, namely in the course of the curing process of the2-cyanoacrylate-based composition.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

Coloring Materials

As the coloring material for use in the present invention, pH indicatorsthat change color with change of pH or compounds having such propertiesare preferably used. Among them, those having a color change region in arange of pH 1 to 4 are more preferable since the color change ispossible when 2-cyanoacrylate is cured. Among them, particularlypreferred are those having an indicator color change region that partlyor wholly falls under pH 1 to 4 such that a color of good visibility isexhibited on the acidic side whilst it turns, on the alkaline side,completely colorless or lighter color than the acidic side. When suchcoloring materials are used, color change is possible in a manner that acolor is visible before the change of color, and the color becomes lessvisible, namely, colorless or light-colored after the change of color.

Furthermore, not only the 2-cyanoacrylate-based composition that iscolored before curing and turns colorless or light-colored after curing,which is the original object of the present invention, but also a2-cyanoacylate-based composition that is colorless or light-coloredbefore curing and turns colored after curing or a 2-cyanoacrylate-basedcomposition that is colored both before and after curing but exhibitsone color before curing and another color after curing can be used forvarious purposes. These compositions can be obtained by selecting andincorporating a suitable one from the coloring materials that changecolor with pH.

For example, when a coloring material, which has no pH indication coloron the acidic side and thus is transparent and colorless upon additionto a 2-cyanoacrylate that has not been cured, but develops color at pH2.5 to 5, is used, the resultant 2-cyanoacrylate turns from colorless tocolored when it is cured.

Concrete examples of the coloring material for use in the presentinvention include bromocresol green, bromocresol purple, bromothymolblue, bromophenol blue, bromophenol red, m-cresol purple, o-cresol red,methyl yellow, methyl red, methyl orange, methyl violet, pentamethoxyred, pyrogallol red, thymol blue, and the like.

Among them, a preferred type is a coloring material that turnslight-colored after 2-cyanoacrylate is cured compared to before curing,and includes methyl yellow, methyl red and the like. A more preferredtype is a coloring material that turns colorless after curing, whichincludes pentamethoxy red and the like.

These coloring materials can be used as agents for determining curing of2-cyanoacrylates. In addition, determination of the curing of2-cyanoacrylates can be made by blending these coloring materials with2-cyanoacrylates.

Amount of the coloring material to be blended with the 2-cyanoacrylatecan not generally be defined, as extent of coloring varies dependingupon types of coloring materials, but is, in ordinary cases, preferablyfrom 0.5 to 1,500 ppm by weight (hereinafter referred only to ppm unlessotherwise specified), more preferably from 5 to 500 ppm. A larger amountthan above adversely affects curability of 2-cyanoacrylates and asmaller amount than above is not preferable due to too weak coloring andless visibility.

2-Cyanoacrylates

2-Cyanoacrylates whose workability can be improved using the coloringmaterial of the present invention are cyanoacrylate derivatives whichare used for adhesive, filling, surface treatment agents or the like.

Examples thereof include methyl-2-cyanoacrylate, ethyl-2-cyanoacrylate,propyl-2-cyanoacrylate, isopropyl-2-cyanoacrylate,butyl-2-cyanoacrylate, isobutyl-2-cyanoacrylate, amyl-2-cyanoacrylate,hexyl-2-cyanoacrylate, cyclohexyl-2-cyanoacrylate,octyl-2-cyanoacrylate, 2-ethylhexyl-2-cyanoacrylate,allyl-2-cyanoacrylate, propargyl-2-cyanoacrylate,phenyl-2-cyanoacrylate, benzyl-2-cyanoacrylate,methoxyethyl-2-cyanoacrylate, ethoxyethyl-2-cyanoacrylate,tetrahydrofulfuryl-2-cyanoacrylate, 2-chloroethyl-2-cyanoacrylate,3-chloropropyl-2-cyanoacrylate, 2-chlorobutyl-2-cyanoacrylate,2,2,2-trifluoroethyl-2-cyanoacrylate,hexafluoroisopropyl-2-cyanoacrylate, or the like.

These 2-cyanoacrylates may be used singly to prepare adhesive, fillingor surface treatment compositions or agents, or two or more2-cycanoacrylates may be used as an admixture.

Other Components

The 2-cyanoacrylate-based composition of the present invention comprisesa coloring material and a 2-cyanoacrylate as essential components.However, when the composition is used as an adhesive, it is supplementedwith an anion polymerization stabilizer, a radical polymerizationstabilizer, a thickener, a curing accelerator, a plasticizer and athixotropic agent, as required.

The anion polymerization stabilizer may be an anion polymerizationstabilizer that is conventionally known in the art, and includes sulfurdioxide, nitrogen monoxide, hydrogen fluoride, sultone compounds,BF₃-ether complex, BF₃-aceticacid complex or BF₃-methanol complex,methansulfonic acid, p-toluenesulfonic acid and the like. Generally, theamount thereof to be added is preferably in the range from 1 ppm byweight to 1% by weight. As described later, these compounds greatlyinfluence the performance of change of color, and thus it is importantto select a suitable amount depending on coloring materials to becombined.

The anion polymerization stabilizers are generally acidic compounds.Besides, the 2-cyanoacrylate-based composition contains various acidiccompounds such as impurities derived from depolymerization catalystsmixed in the synthetic process, and impurities derived from distillationstabilizers. The color change of the pH indicators used in the presentinvention is affected by the type, the amount to be added or the like ofthese acidic compounds. For example, when BF₃-ether complex, BF₃-aceticacid complex, BF₃-methanol complex or the like is used as an anionpolymerization stabilizer, the pH required for coloring materials tendsto shift a little to the acidic side (that is, the color change regionshifts to the acidic side). Furthermore, the acidic compounds greatlyinfluence curing speed and product life of 2-cyanoacrylate-basedcompositions. Thus, it is important to select their suitable amounts tobe added and combination taking into account target curing performance,product life, color change performance and various other aspects.

The radical polymerization stabilizer may be a radical polymerizationstabilizer that is conventionally known in the art, and specificallyincludes hydroquinone, hydroquinone monomethyl ether, catechol,pyrogallol and the like. Preferable amount thereof to be added is in therange of 1 ppm by weight to 1% by weight.

In order to increase adhesion speed, anion polymerization acceleratorsmay be added, which include polyalkylene oxides and their derivatives,crown ethers and their derivatives, silacrown ethers and theirderivatives, calixarene derivatives, thiacalixarene derivatives and thelike.

The thickener may be a thickener that is conventionally known in theart, and specifically includes polymethylmethacrylate, methylmethacrylate/acrylate copolymers, methyl methacrylate/methacrylatecopolymers, cellulose derivatives and the like. Preferable amountthereof to be added is in the range of 0.1 to 20% by weight.

The plasticizer may be a plasticizer that is conventionally known in theart, and includes alkyl phthalates, specific multifunctional(meth)acrylates and the like. Preferable amount thereof to be added isin the range of 0.01 to 30% by weight.

The thixotropic agent may be a thixotropic agent that is conventionallyknown in the art, and specifically includes hydrophobic silica.Preferable amount thereof to be added is in the range of 0.1 to 20% byweight.

Besides, adhesion-imparting agents, perfumes, fillers, crosslinkingagents, tougheners, polymerization initiators, organic solvents or thelike are added depending on purposes. All the known techniquesconcerning these additives can be applied to the 2-cyanoarylate-basedcomposition of the present invention.

The 2-cyanoacrylate-based composition preferred in the present inventionis characterized in that it is colored before curing and turns colorlessor light-colored after curing. For example, when-sulfur dioxide is usedas an anion polymerization stabilizer, this change is considered due tothe fact that pH in the system changes from a pH of approximately 2 to 3before curing to a pH of approximately 3.5 to 4.5 after curing, in viewof change of an added indicator. This change of pH is mainly caused bythe fact that water content is maintained in the range of from severaltens to several hundreds ppm before curing, but the water content in thesystem increases to several thousands ppm or more after curing. Inaddition to this, other factors to lower the acidity are involved, suchas decrease of the anion polymerization stabilizer during curing anddissolution of impurities on the surface of substrates to be bonded.

The acidity of the 2-cyanoacrylate-based composition that is typicallystrongly acidic in the system due to a polymerization inhibitor is alittle reduced by these changes. It is presumed that when a suitable pHindicator which color change region partly or wholly overlaps pH 1 to 4is blended with the system, the composition exhibits a color of theacidic side of the blended coloring material before curing, and a colorof the alkaline side thereof after curing.

Moreover, the cured product of the 2-cyanoacrylate-based compositionafter curing is estimated to have a pH corresponding to 2.5 to 5.Therefore, some pH indicators, which have no color change region withinthe above pH of 1 to 4 or exhibit no color in a water-deficient statebefore curing, exhibit color at the pH of 2.5 to 5 in the cured productof the 2-cyanoacrylate-based composition. Utilizing these properties, itis possible to achieve change of colors from colored state to colorlessstate, from colored state to colored state, or from colorless state tocolored state as described above.

Hereinafter, the present invention will be described further in detailwith reference to examples and comparative examples, but the presentinvention is not limited to these examples.

Methods of evaluation were as follows:

(1) Measuring Method of Set Time

The set time was measured according to JIS K 6861-1995 using test piecesmade of a rigid polyvinyl chloride resin.

(2) Measuring Method of Adhesion Strength

(Rigid Polyvinyl Chloride Resin)

Test pieces made of a rigid polyvinyl chloride resin having a dimensionto be used for the tensile shear adhesion strength test according to JISK 6861-1995 were glued together with an adhesive composition, cured for24 hours and then subjected to the tensile shear adhesion strength test.

(3) Appearance

(Appearance of Liquid)

In order to observe appearance of liquid in coated state, a liquid wascoated on a white polyacetal resin sheet in a thickness of about 0.5 mm,which is similar to the state where one drop (about 0.02 g) was coatedon a substrate, and then appearance was observed.

(Appearance of Cured Product)

Similar to the above for the appearance of liquid in coated state, aliquid was coated on a white polyacetal resin sheet in a thickness ofabout 0.5 mm, and after it was stood for 24 hours at 25° C.×60% RH andcompletely cured, appearance was observed.

EXAMPLE 1

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred with ethyl-2-cyanoacrylate (supplemented with 50 ppm of sulfurdioxide) to make the content of pentamethoxy red 1 ppm, and was used forthe above described evaluation. The results were shown in Table 1.

EXAMPLE 2

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred with the same ethyl-2-cyanoacrylate as Example 1 to make the contentof pentamethoxy red 10 ppm, and was used for the above describedevaluation. The results were shown in Table 1.

EXAMPLE 3

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred with the same ethyl-2-cyanoacrylate as Example 1 to make the contentof pentamethoxy red 100 ppm, and was used for the above describedevaluation. The results were shown in Table 1.

EXAMPLE 4

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred with the same ethyl-2-cyanoacrylate as Example 1 to make the contentof pentamethoxy red, 1,000 ppm, and was used for the above describedevaluation. The results were shown in Table 1.

EXAMPLE 5

A 2-cyanoacrylate-based composition was prepared by mixing bromothymolblue with the same ethyl-2-cyanoacrylate as Example 1 to make thecontent of bromothymol blue 10 ppm, and was used for the above describedevaluation. The results were shown in Table 1.

EXAMPLE 6

A 2-cyanoacrylate-based composition was prepared by mixing bromothymolblue with the same ethyl-2-cyanoacrylate as Example 1 to make thecontent of bromothymol blue 100 ppm, and was used for the abovedescribed evaluation. The results were shown in Table 1.

EXAMPLE 7

A 2-cyanoacrylate-based composition was prepared by mixing bromothymolblue with the same ethyl-2-cyanoacrylate as Example 1 to make thecontent of bromothymol blue 1,000 ppm, and was used for the abovedescribed evaluation. The results were shown in Table 1.

EXAMPLE 8

A 2-cyanoacrylate-based composition was prepared by mixing methyl yellowwith the same ethyl-2-cyanoacrylate as Example 1 to make the content ofmethyl yellow 10 ppm, and was used for the above described evaluation.The results were shown in Table 1.

EXAMPLE 9

A 2-cyanoacrylate-based composition was prepared by mixing methyl yellowwith the same ethyl-2-cyanoacrylate as Example 1 to make the content ofmethyl yellow 100 ppm, and was used for the above described evaluation.The results were shown in Table 1.

EXAMPLE 10

A 2-cyanoacrylate-based composition was prepared by mixing methyl yellowwith the same ethyl-2-cyanoacrylate as Example 1 to make the content ofmethyl yellow 1,000 ppm, and was used for the above describedevaluation. The results were shown in Table 1.

EXAMPLE 11

A 2-cyanoacrylate-based composition was prepared by pentamethoxy redwith ethyl-2-cyanoacrylate (supplemented with 100 ppm of BF₃-methanolcomplex) to make the content of pentamethoxy red 100 ppm, and was usedfor the above described evaluation. The results were shown in Table 1.

EXAMPLE 12

A 2-cyanoacrylate-based composition was prepared by mixing bromothymolblue with the same ethyl-2-cyanoacrylate as Example 11 to make thecontent of bromothymol blue 100 ppm, and was used for the abovedescribed evaluation. The results were shown in Table 1.

EXAMPLE 13

A 2-cyanoacrylate-based composition was prepared by mixing methyl yellowwith the same ethyl-2-cyanoacrylate as Example 11 to make the content ofmethyl yellow 100 ppm, and was used for the above described evaluation.The results were shown in Table 1.

EXAMPLE 14

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred with isopropyl-2-cyanoacrylate (supplemented with 50 ppm of sulfurdioxide) to make the content of pentamethoxy red 100 ppm, and was usedfor the above described evaluation. The results were shown in Table 1.

EXAMPLE 15

A 2-cyanoacrylate-based composition was prepared by mixing bromothymolblue with the same isopropyl-2-cyanoacrylate as Example 14 to make thecontent of bromothymol blue 100 ppm, and was used for the abovedescribed evaluation. The results were shown in Table 1.

EXAMPLE 16

A 2-cyanoacrylate-based composition was prepared by mixing methyl yellowwith the same isopropyl-2-cyanoacrylate as Example 14 to make thecontent of methyl yellow 100 ppm, and was used for the above describedevaluation. The results were shown in Table 1.

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred with ethoxyethyl-2-cyanoacrylate (supplemented with 50 ppm of sulfurdioxide) to make the content of pentamethoxy red 100 ppm, and was usedfor the above described evaluation. The results were shown in Table 1.

EXAMPLE 18

A 2-cyanoacrylate-based composition was prepared by mixing bromothymolblue with the same ethoxyethyl-2-cyanoacrylate as Example 17 to make thecontent of bromothymol blue 100 ppm, and was used for the abovedescribed evaluation. The results were shown in Table 1.

EXAMPLE 19

A 2-cyanoacrylate-based composition was prepared by mixing methyl yellowwith the same ethoxyethyl-2-cyanoacrylate as Example 17 to make thecontent of methyl yellow 100 ppm, and was used for the above describedevaluation. The results were shown in Table 1.

EXAMPLE 20

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred and crown ether O-18 with the same ethyl-2-cyanoacrylate as Example11 to make the content of pentamethoxy red 50 ppm and the content ofcrown ether O-18 500 ppm, and was used for the above describedevaluation. The results were shown in Table 1.

EXAMPLE 21

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred, crown ether O-18 and polymethylmethacrylate (molecular weight1,000,000) with the same ethyl-2-cyanoacrylate as Example 11 to make thecontent of pentamethoxy red 50 ppm, the content of crown ether O-18 500ppm and the content of polymethylmethacrylate 4% by weight, and was usedfor the above described evaluation. The results were shown in Table 1.

EXAMPLE 22

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred, crown ether O-18 and dipentaerythritol hexaacrylate with the sameethyl-2-cyanoacrylate as Example 11 to make the content of pentamethoxyred 50 ppm, the content of crown ether O-18 500 ppm and the content ofdipentaerythritol hexaacrylate 5% by weight, and was used for the abovedescribed evaluation. The results were shown in Table 1.

EXAMPLE 23

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred, crown ether O-18 and dimethyl phthalate with the sameethyl-2-cyanoacrylate as Example 11 to make the content of pentamethoxyred 50 ppm, the content of crown ether O-18 500 ppm and the content ofdimethyl phthalate 5% by weight, and was used for the above describedevaluation. The results were shown in Table 1.

EXAMPLE 24

A 2-cyanoacrylate-based composition was prepared by mixing pentamethoxyred, crown ether O-18 and acetyl tributyl citrate with the sameethyl-2-cyanoacrylate as Example 11 to make the content of pentamethoxyred 50 ppm, the content of crown ether O-18 500 ppm and the content ofacetyl tributyl citrate 5% by weight, and was used for the abovedescribed evaluation. The results were shown in Table 1.

COMPARATIVE EXAMPLE 1

Ethyl-2-cyanoacrylate with which no coloring material was blended(supplemented with 50 ppm of sulfur dioxide) was used for the abovedescribed evaluation. The results were shown in Table 1.

COMPARATIVE EXAMPLE 2

Ethyl-2-cyanoacrylate with which no coloring material was blended(supplemented with 100 ppm of BF₃-methanol complex) was used for theabove described evaluation. The results were shown in Table 1.

COMPARATIVE EXAMPLE 3

Isopropyl-2-cyanoacrylate with which no coloring material was blended(supplemented with 50 ppm of sulfur dioxide) was used for the abovedescribed evaluation. The results were shown in Table 1.

COMPARATIVE EXAMPLE 4

Ethoxyethyl-2-cyanoacrylate with which no coloring material was blended(supplemented with 50 ppm of sulfur dioxide) was used for the abovedescribed evaluation. The results were shown in Table 1.

COMPARATIVE EXAMPLE 5

An adhesive composition was prepared by mixing Macrolex Red (trade nameof Bayer AG) with the same ethyl-2-cyanoacrylate as Comparative Example1 to make the content of the Macrolex Red 100 ppm, and was used for theabove described evaluation. The results were shown in Table 1.

COMPARATIVE EXAMPLE 6

An adhesive composition was prepared by mixing Macrolex Red with thesame ethyl-2-cyanoacrylate as Comparative Example 2 to make the contentof the Macrolex Red 100 ppm, and was used for the above describedevaluation. The results were shown in Table 1.

COMPARATIVE EXAMPLE 7

An adhesive composition was prepared by mixing Macrolex Red with thesame isopropyl-2-cyanoacrylate as Comparative Example 3 to make thecontent of the Macrolex Red 100 ppm, and was used for the abovedescribed evaluation. The results were shown in Table 1.

COMPARATIVE EXAMPLE 8

An adhesive composition was prepared by mixing Macrolex Red with thesame ethoxyethyl-2-cyanoacrylate as Comparative Example 4 to make thecontent of the Macrolex Red 100 ppm, and was used for the abovedescribed evaluation. The results were shown in Table 1.

TABLE 1 Rigid PVC adhesion test Adhesion strength Set time (N/mm²)Appearance (sec) Initial Liquid Cured product Example 1 10 3.3 Lightpurple Colorless Example 2 10 3.3 Purple Colorless Example 3 5 3.3Purple Colorless Example 4 5 3.2 Deep purple Light purple Example 5 103.3 Colorless Light yellow Example 6 10 3.2 Colorless Yellow Example 720 3.0 Colorless Yellow Example 8 10 3.2 Red Yellow Example 9 5 3.3 RedYellow Example 10 3 3.1 Red Yellow Example 11 5 3.3 Purple ColorlessExample 12 10 3.3 Colorless Yellow Example 13 5 3.3 Red Yellow Example14 10 3.2 Purple Colorless Example 15 20 3.1 Colorless Yellow Example 165 3.2 Red Yellow Example 17 20 3.1 Purple Colorless Example 18 30 3.0Colorless Yellow Example 19 10 3.0 Red Yellow Example 20 3 3.3 PurpleColorless Example 21 3 3.3 Purple Colorless Example 22 3 2.8 PurpleColorless Example 23 3 2.9 Purple Colorless Example 24 3 3.1 PurpleColorless Comparative 5 3.2 Colorless Colorless Example 1 Comparative 53.3 Colorless Colorless Example 2 Comparative 10 3.1 Colorless ColorlessExample 3 Comparative 20 3.1 Colorless Colorless Example 4 Comparative10 3.2 Red Red Example 5 Comparative 10 3.3 Red Red Example 6Comparative 20 3.1 Red Red Example 7 Comparative 30 2.9 Red Red Example8

As shown in each Example in Table 1, it has been found that the2-cyanoacrylate-based composition of the present invention has differentcolors between before and after curing. Moreover, it has been found thatthe curing performance of the composition mixed with a coloring materialin a suitably selected amount can be maintained at the same level asthat of the composition mixed with no coloring material.

On the other hand, in comparative examples in Table 1, all compositionsare transparent and colorless both before and after curing when nocoloring material is added. Moreover, when any coloring material isadded, all compositions are colored in the same color both before andafter curing, and the color change effect of the present invention wasnot be observed.

INDUSTRIAL APPLICABILITY

The preferable 2-cyanoacrylate-based composition of the presentinvention is excellent in visibility and workability as it is coloredbefore curing, and provides bonded, filled or surface treated portionswith good appearance as it becomes colorless or light-colored aftercuring. For this reason, the composition has excellent workability aswell as good finished-quality. Thus, it provides coating workability andcurability that are balanced in a high level for industries andhouseholds, particularly for applications in which accuracy is required.Further, since the composition allows good work, it can be used furtherwidely in various fields. Furthermore, even when the composition is usedby consumers poor in knowledge of adhesion, filling or surfacetreatment, the location and amount of application can be easilydetermined and they can work without any concern about the finishedquality of the exposed part of the composition. So, the compositionprovides excellent usability and gives great effect to variousindustries.

1. A method for determining curing of 2-cyanoacrylates, which consistsessentially of blending, with a 2-cyanoacrylate, a coloring materialthat changes color with curing of the 2-cyanoacrylate, and curing theblend whereby curing is determined by said coloring material changingcolor, wherein the coloring material is a compound having a property ofchanging color with a change of pH, wherein the coloring material isselected from methyl yellow, methyl orange, methyl violet, pentamethoxyred and methyl red.
 2. A method for determining curing of2-cyanoacrylates according to claim 1, wherein the coloring material ismethyl yellow.
 3. A method for determining curing of 2-cyanoacrylatesaccording to claim 1, wherein the coloring material is methyl orange. 4.A method for determining curing of 2-cyanoacrylates according to claim1, wherein the coloring material is methyl violet.
 5. A method fordetermining curing of 2-cyanoacrylates according to claim 1, wherein thecoloring material is pentamethoxy red.
 6. A method for determiningcuring of 2-cyanoacrylates according to claim 1, wherein the coloringmaterial is methyl red.
 7. A method for preparing a cured adhesivecomposition which consists essentially of blending, with a2-cyanoacrylate, a coloring material that changes color with curing ofthe 2-cyanoacrylate, and curing the blend whereby curing is determinedby said coloring material changing color, wherein the coloring materialis a compound having a property of changing color with a change of pH,wherein the coloring material is selected from methyl yellow, methylorange, methyl violet, pentamethoxy red and methyl red.
 8. A method forpreparing a cured adhesive composition according to claim 7, wherein thecoloring material is methyl yellow.
 9. A method for preparing a curedadhesive composition according to claim 7, wherein the coloring materialis methyl orange.
 10. A method for preparing a cured adhesivecomposition according to claim 7, wherein the coloring material ismethyl violet.
 11. A method for preparing a cured adhesive compositionaccording to claim 7, wherein the coloring material is pentamethoxy red.12. A method for preparing a cured adhesive composition according toclaim 7, wherein the coloring material is methyl red.